A primitive procedure was proposed for evaluating earthquake response spectra of large-event motions to make use of records from smaller events. The result of the regression analysis of the response spectra was utilized to obtain the site amplification factors in the proposed procedure, and the formulation of the seismic-source term in the regression analysis was examined. A linear form of the moment magnitude, Mω, is good for scaling the source term of moderate earthquakes with Mω of 5.5 to 7.0, while a quadratic form of Mω and the ω-square source-spectrum model is appropriate for scaling the source term of smaller and greater earthquakes, respectively.
